Capacity neutralized switch



CAPACITY NEUTRALIZED SWITCH Filed Jan. 2v 1927 NEE/FER INVENTOR LB MOULTON ray/Z1 d ORNEY Patented June 10, 1930 UNITED STATES PATENT OFFICE ALBERT B. IOULTON, OF RIVEBHEAD, NEW YORK, ASSIGNOR T RADIO CORPORATION OF AMERICA, A CORPORATION OF DELAWARE CAPACITY NEUTRALIZED SWITCH Application filed January 27, 1927. Serial No. 163,887.

This invention relates to capacity neutralization of switching devices, and more particularly to a method and means for p1'ov1d ing a capacity neutralized switch for the control of very high frequency energy.

0 switch, and its contacts.

It is found that an appreciable amount of high frequency energy will traverse an open switch, because of the natural capacity which exists between the contactors or poles of the In the case of transmission energy there may be considerable radiation when even an ordinary type of knife-switch has been opened. In connection with high frequency receivers switching 1s often imperfect because one very convement type of switch frequently used for this purpose possesses a rather h gh nherent capac ity, and consequently a disconnected antenna or wire line may effect appreciable response in its receiver.

It is an object of my invention to prevent the transfer of high frequency energy over an open switch. This I propose to do by applying oppositely phased neutralizing ener y to the dead side of the SWItCh: Structurafiy, this is most easily accomplished by connecting the opposite side of the line to the dead side of the switch through a neutralizing capacity which isequal 1n magn tude to the natural capacitance of the open switch. I

It is a furtherobject of my invention to provide the necessary neutraliz ng capacitances ina simple and convenient manner, and to do this I employ a double throw switch instead of a single throw switch, and use the extra contacts of the double throw switch to form the desired neutralizing capacitance with respect to the contactor or pole of the switch.

In the drawing accompany ng the-specification,

Fig. 1 is a wiring diagram showing one method of neutralizing 'the capacity of a double pole single throw switch;

Fig.2 illustrates how a double pole double throw switch may be employed to providea capacity neutralized switch; and

Fig. 3 is a'modification.

Referring to Fig. 1, the conductors 2 and 4 are connected to a source of high frequency" energy, while the conductors 6 and 8 are con nccted to means to utilize such energy. The switch comprises poles 9 and 10, and the contacts l2 and 14. \V'hen the switch is open there is a natural capacitance 0 between the pole 9 and the contact 12, and a capacitance 0 between the pole 10 and the contact 14:, through which high frequencyenergy may pass from the source to the line 6, 8, and to prevent this the neutralizing capacitance 01,, equal to 0 is connected as shown, between the contact l i and the pole 9, and the neutralizing capacitance n equal to the natural capacitance 0 is connected from the contact 12 to the pole 10. Since the polarity of the conductors 2 and 4: is opposite, it is clear that potentials will be applied to the dead side of the switch through the neutralizing condensers which are of opposite sign to those applied through the natural capacitances, and therefore the switch when opened will prevent the flow of high frequency energy to the line 6, 8.

The preceding description is of the more general case in which 0 need not necessarily equal 0 Of course, in practice, these usually will be equal in value, and therefore the neutralizing condensers n, and n, will also be equal in value, in which case the conductors 6, 8 may be made the live side of the switch and conductors 2, 4, the dead side of the switch, as well as vice versa.

I find that-a very simple way of providing the roper neutralizing condensers is to use in p ace of a double pole single throw switch such as was shown in Figure 1, a double polo double throw switch as shown in 'Figure 2. In this modification, as in the preceding, the conductors 2, 4 are one line, while the conductors 6, 8 are the other line. If the contacts 12, 19 are considered equivalent to the contacts 12', 14 in Figure 1, then the contacts 16 and '18 may be considered as neutralizing contacts, for they form, together withthe poles or contactors 9, 16, capacitances n, and n, which are equal to the capacitances c and 0 for structural reasons. The c0ntacts'12, 19 are cross connected with the contacts 16, 18 by means of-the conductors 20 and 22. The line conductor 2 has been shown connected to the contact 16 instead of the contact 19 for the reason that it is preferable to have the connections symmetrical with respect to the poles. It would, of course, be possible to connect the line 2, 4 to the contact 16, 18, or 12, 19, or 18, 19, as well as to 12, 16 as shown. Either line may be the supply or utilization line.

In the case of telephony by means of a high frequency carrier wave, difficulty is experienced in using the usual type of operating switch. The same type of switch is frequently used for the switching of radio receivers with respect to receiving antennae, and there, too, the problem of neutralization must be contended with, for the parallel contactor and contact plates of these switches possess considerable inherent capacitance. Such a switch has been schematically represented in Figure 3. The line 2, 4 is connected to either an antenna or an incoming wire line, while the line 6, 8 is connected as shown, to the input side of any suitable reeeiver or amplifier, typified in this instance by a stage of push-pull amplification. The natural capacitances 0 and 0 are counteracted by the capacitanees 12, and 12 as clearly shown in the diagram. The contactors 9 and 10 are actuated by any suitable operating toggle 30, pivoted at 32, through the insulating rollers 34.

The foregoing is disclosed by way of illustration, and not limitation, of my invention, which I claim is:

1. The method of preventing a transfer of high frequency energy thru an open mechanical switch because of its natural capacitance which consists in applying oppositely phased neutralizing energy to the dead side of the switch.

2. The combination with a high frequency circuit and a mechanical switch having natural capacitance of a neutralizing condenser for neutralizing the natural capacitance of the switch.

3. The combination with a high frequency circuit and a mechanical switch for its control of a neutralizing condenser arranged to counteract the natural capacitance of the switch when the switch is opened.

4:. A capacity neutralized switch for controlling very high frequency currents comprising a plurality of contactors, a plurality of contacts for cooperation therewith to control the current, and a plurality of neutralizing elements which form with the eontactors neutralizing condensers equivalent to the natural capacitances between the contactors and contacts, and means to impress upon the neutralizing condensers potentials opposite in phase to those impressed upon the natural capacitances.

5. The combination with a two pole me chanical switch of a condenser substantially equal in magnitude to the natural capacitance between a pole and its contact, connected between the pole and the contact of the other pole.

6. The combination with a two pole mechanicalswitch of a pair of condensers substantially equal in magnitude to the natural capacitance between each pole and its contact, connected between each pole and the contact of the other pole 7. The combination with a high frequency circuit of a mechanical switch comprising structurally a double throw switch each havlng two of its contacts form with their respective eontactors a neutralizing condenser for counteracting the effect of the inherent capacitance between the other respective contactors and their contacts.

8. A capacity neutralized switch for controlling very high frequency currents comprising structurally a double pole double throw switch and conductors for cross connecting its contacts, whereby the contacts form opposed capacitances with reference to the poles.

9. In combination, a supply circuit for high frequency energy, a utilization circuit for the high frequency energ and means to connect or disconnect the supply circuit to the utilization circuit comprising a double pole double throw switch, means connecting one of said circuits to two of the switch contacts, means connecting the other of said circuits to the switch poles, and means cross eonnecting the contacts, whereby the contacts torm opposed capa-citances with reference to the poles in order to prevent energy transfer through the switch when open.

. A. B. MOULTON. 

